FprEN ISO 20846

Petroleum and related products - Determination of sulfur content of automotive fuels - Ultraviolet fluorescence method (ISO/FDIS 20846:2026)

This document specifies an ultraviolet (UV) fluorescence test method for the determination of the sulfur content of the following products:
— having sulfur contents in the range 3 mg/kg to 500 mg/kg,
— motor gasolines containing up to 3,7 % (m/m) oxygen [including those blended with ethanol up to about 10 % (V/V)],
— diesel fuels, including those containing up to about 30 % (V/V) fatty acid methyl ester (FAME),
— having sulfur contents in the range of 3 mg/kg to 45 mg/kg,
— synthetic fuels, such as hydrotreated vegetable oil (HVO) and gas to liquid (GTL).
Other products can be analysed and other sulfur contents can be determined according to this test method, however, no precision data for products other than automotive fuels and for results outside the specified range have been established for this document. Halogens interfere with this detection technique at concentrations above approximately 3 500 mg/kg.
NOTE 1 Some process catalysts used in petroleum and chemical refining can be poisoned when trace amounts of sulfur-bearing materials are contained in the feedstocks.
NOTE 2 This test method can be used to determine sulfur in process feeds and can also be used to control sulfur in effluents.
NOTE 3 For the purposes of this document, "% (m/m)" and "% (V/V)" are used to represent the mass fraction, w, and the volume fraction, φ, of a material respectively.
NOTE 4 Sulfate species in ethanol do not have the same conversion factor of organic sulfur in ethanol. Nevertheless, sulfates have a conversion factor close to that of organic sulfur.
NOTE 5 Nitrogen interference can occur, see 6.5 for further guidance.

Mineralölerzeugnisse - Bestimmung des Schwefelgehaltes von Kraftstoffen - Ultraviolettfluoreszenz-Verfahren (ISO/FDIS 20846:2026)

Dieses Dokument legt ein Ultraviolett(UV)-fluoreszenz-Prüfverfahren zur Bestimmung des Schwefelgehaltes von folgenden Erzeugnissen fest:
   mit Schwefelgehalten im Bereich von 3 mg/kg bis 500 mg/kg:
   Ottokraftstoffe, die Sauerstoff bis zu einem Massenanteil von 3,7 % (3,7 % (m/m)) enthalten [einschließlich solcher mit einem beigemischten Volumenanteil von Ethanol bis zu etwa 10 % (10 % (V/V))];
   Dieselkraftstoffe, einschließlich solcher, die bis zu etwa 50 % (Volumenanteil) Fettsäure-Methylester (FAME, en: fatty acid methyl ester) enthalten;
   mit Schwefelgehalten im Bereich von 3 mg/kg bis 45 mg/kg:
   synthetische Kraftstoffe, z. B. hydriertes Pflanzenöl (HVO, en: hydrotreated vegetable oil) und „Gas to Liquid“ (GTL);
   mit Schwefelgehalten im Bereich von 3 mg/kg bis 30 mg/kg:
   reines FAME (B100) und Dieselkraftstoffe mit einem Volumenanteil von mehr als 50 % FAME.
Andere Erzeugnisse (z. B. Raffinerie-Zwischenprodukte und Abfallströme) und andere Schwefelgehalte können mit diesem Prüfverfahren untersucht werden, jedoch wurden die in diesem Dokument angegebenen Präzisionsangaben nur für Kraftstoffe für Kraftfahrzeuge für den angegebenen Bereich ermittelt. Halogene, die in Konzentrationen oberhalb von etwa 3 500 mg/kg vorliegen, stören die Bestimmung.

Produits pétroliers et connexes - Détermination de la teneur en soufre des carburants pour automobiles - Méthode par fluorescence ultraviolette (ISO/FDIS 20846:2026)

Le présent document spécifie une méthode par fluorescence ultra-violette (FUV) pour le dosage du soufre dans les produits suivants:
— ceux dont la teneur en soufre est comprise dans l'intervalle de 3 à 500 mg/kg:
— les essences automobiles contenant jusqu'à 3,7 % (m/m) en oxygène [les mélanges avec de l'éthanol jusqu'à environ 10 % (V/V) inclus],
— les carburants diesel, dont ceux contenant jusqu'à 30 % (V/V) d'esters méthyliques d'acides gras.
— ceux dont la teneur en soufre est comprise dans l'intervalle de 3 à 45 mg/kg:
— les carburants synthétiques, tels que les huiles végétales hydrogénées (HVO) et les carburants liquides produits à partir de gaz («gas to liquid», GTL).
D'autres produits peuvent être analysés et d'autres teneurs en soufre peuvent être déterminées suivant cette méthode, cependant, il n'a pas été établi de données de fidélité pour des produits autres que les carburants pour automobiles et pour des résultats en dehors de la gamme spécifiée pour le présent document. Les halogènes, à des concentrations supérieures à environ 3 500 mg/kg, interfèrent.
NOTE 1 Certains catalyseurs utilisés dans le raffinage chimique et pétrolier peuvent être pollués lorsque des composés soufrés sont présents en trace dans les charges.
NOTE 2 Cette méthode peut être utilisée pour déterminer la teneur en soufre des charges et peut aussi être utilisée pour contrôler la teneur en soufre des effluents.
NOTE 3 Pour les besoins du présent document, «% (m/m)» et «% (V/V)» sont utilisés pour désigner respectivement la fraction massique, w, et la fraction volumique, φ, d'un produit.
NOTE 4 Le facteur de conversion des sulfates dans l'éthanol n'est pas le même que celui des composés organiques sulfurés dans l'éthanol. Ils sont cependant proches.
NOTE 5 Une interférence avec l'azote peut avoir lieu, voir 6.5 pour plus de précisions.

Naftni in sorodni proizvodi - Določanje žvepla v gorivih za motorna vozila - Ultravijolična fluorescenčna metoda (ISO/FDIS 20846:2026)

General Information

• Status: Not Published
• Publication Date: 30-Aug-2026
• ICS: 75.160.20 - Liquid fuels
• ICS: 75.160.30 - Gaseous fuels
• Technical Committee: CEN/TC 19 - Petroleum products, lubricants and related products
• Drafting Committee: CEN/TC 19/WG 27 - Elemental analysis of petroleum and related products
• Current Stage: 5020 - Submission to Vote - Formal Approval
• Start Date: 02-Apr-2026
• Completion Date: 02-Apr-2026
• Ref Project: kSIST FprEN ISO 20846:2026 - Petroleum and related products - Determination of sulfur content of automotive fuels - Ultraviolet fluorescence method (ISO/FDIS 20846:2026)

Relations

• Consolidated By: ISO/FDIS 20846 - Petroleum and related products — Determination of sulfur content of automotive fuels — Ultraviolet fluorescence method
• Effective Date: 12-Feb-2026
• Revises: EN ISO 20846:2019 - Petroleum products - Determination of sulfur content of automotive fuels - Ultraviolet fluorescence method (ISO 20846:2019)
• Effective Date: 26-Jul-2023

Overview

FprEN ISO 20846: Petroleum and Related Products - Determination of Sulfur Content of Automotive Fuels - Ultraviolet Fluorescence Method sets out a standardized procedure for measuring sulfur content in a range of automotive fuels. Developed by CEN and aligned with ISO/FDIS 20846:2026, this standard applies the ultraviolet (UV) fluorescence method to quantify sulfur concentrations in motor gasolines, diesel fuels (with FAME blends), and synthetic fuels like hydrotreated vegetable oil (HVO) and gas-to-liquid (GTL) fuels. The method is suitable for sulfur levels ranging from 3 mg/kg up to 500 mg/kg, with established precision for automotive fuels and lower concentration ranges for advanced blends and synthetic alternatives.

Key Topics

• Sulfur Detection Range: This standard covers the determination of sulfur in automotive fuels within 3 mg/kg to 500 mg/kg, including:

  • Motor gasolines with up to 3.7% oxygen content, such as those blended with up to 10% ethanol.
  • Diesel fuels containing up to 30% FAME (fatty acid methyl esters), with specified precision for 3 mg/kg to 45 mg/kg sulfur.
  • Synthetic fuels, such as HVO and GTL, validated within the 3 mg/kg to 45 mg/kg sulfur range.

• Test Principle: The sample is combusted at high temperatures (1000°C to 1100°C) in an oxygen-rich environment, converting sulfur to sulfur dioxide. The resulting SO₂ is then excited by UV light, and the emitted fluorescence is measured to determine the sulfur content.

• Calibration and Verification: The method specifies robust procedures for calibration, including multi-point and one-point calibration using certified reference standards and quality control samples to ensure accuracy and repeatability.

• Sample Handling: Emphasizes proper sampling, preservation, and preparation procedures to avoid contamination or loss of volatile components, following referenced ISO guidelines (ISO 3170, ISO 3171).

• Interferences and Limitations: Notes the impact of halogens above 3,500 mg/kg and possible nitrogen interference. It cautions users about safety and handling hazardous materials and equipment.

Applications

Implementing FprEN ISO 20846 is essential in the petroleum industry and regulatory compliance for automotive fuels, offering several key benefits:

• Quality Control: Refineries and fuel suppliers rely on this standard to ensure automotive fuels meet stringent sulfur content regulations, protecting engine systems and reducing emissions.
• Process Optimization: The method supports the control of sulfur in process feeds and effluents, crucial for refining operations where catalyst life and product quality are impacted by sulfur levels.
• Compliance with Emission Standards: Accurate sulfur content determination enables fuel suppliers to comply with national and international emissions requirements, contributing to cleaner air and environmental protection.
• Research & Development: The ability to measure a wide range of fuels, including biofuels and synthetic alternatives, supports the shift toward sustainable energy solutions and the development of new fuel formulations.

Related Standards

• ISO 1042: Laboratory glassware - One-mark volumetric flasks.
• ISO 3170 / ISO 3171: Hydrocarbon liquids - Manual and automatic sampling methods.
• ISO 3675 / ISO 12185: Methods for determination of the density of petroleum products.
• ISO 4259 / ISO 4259-1: Precision and bias methods for petroleum and related products.
• ISO 17034: General requirements for the competence of reference material producers.
• EN 228 & EN 590: European standards for unleaded petrol and diesel fuel specifications.

Adopting FprEN ISO 20846 ensures consistency, reliability, and regulatory alignment in sulfur analysis for automotive and synthetic fuels, directly supporting the fuel industry's ongoing quality and sustainability efforts.

Standards Content (Sample)

SLOVENSKI STANDARD
oSIST prEN ISO 20846:2025
01-oktober-2025
Naftni in sorodni proizvodi - Določanje žvepla v gorivih za motorna vozila -
Ultravijolična fluorescenčna metoda (ISO/DIS 20846:2025)
Petroleum and related products - Determination of sulfur content of automotive fuels -
Ultraviolet fluorescence method (ISO/DIS 20846:2025)
Mineralölerzeugnisse - Bestimmung des Schwefelgehaltes von Kraftstoffen -
Ultraviolettfluoreszenz-Verfahren (ISO/DIS 20846:2025)
Produits pétroliers et connexes - Détermination de la teneur en soufre des carburants
pour automobiles - Méthode par fluorescence ultraviolette (ISO/DIS 20846:2025)
Ta slovenski standard je istoveten z: prEN ISO 20846
ICS:
75.160.20 Tekoča goriva Liquid fuels
oSIST prEN ISO 20846:2025 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

oSIST prEN ISO 20846:2025
oSIST prEN ISO 20846:2025
DRAFT
International
Standard
ISO/DIS 20846
ISO/TC 28
Petroleum and related products —
Secretariat: NEN
Determination of sulfur content
Voting begins on:
of automotive fuels — Ultraviolet
2025-08-26
fluorescence method
Voting terminates on:
ICS: 75.160.20; 75.160.30
2025-11-18
THIS DOCUMENT IS A DRAFT CIRCULATED
FOR COMMENTS AND APPROVAL. IT
IS THEREFORE SUBJECT TO CHANGE
AND MAY NOT BE REFERRED TO AS AN
INTERNATIONAL STANDARD UNTIL
PUBLISHED AS SUCH.
This document is circulated as received from the committee secretariat.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL,
TECHNOLOGICAL, COMMERCIAL AND
USER PURPOSES, DRAFT INTERNATIONAL
STANDARDS MAY ON OCCASION HAVE TO
ISO/CEN PARALLEL PROCESSING
BE CONSIDERED IN THE LIGHT OF THEIR
POTENTIAL TO BECOME STANDARDS TO
WHICH REFERENCE MAY BE MADE IN
NATIONAL REGULATIONS.
RECIPIENTS OF THIS DRAFT ARE INVITED
TO SUBMIT, WITH THEIR COMMENTS,
NOTIFICATION OF ANY RELEVANT PATENT
RIGHTS OF WHICH THEY ARE AWARE AND TO
PROVIDE SUPPORTING DOCUMENTATION.
Reference number
ISO/DIS 20846:2025(en)
oSIST prEN ISO 20846:2025
DRAFT
ISO/DIS 20846:2025(en)
International
Standard
ISO/DIS 20846
ISO/TC 28
Petroleum and related products —
Secretariat: NEN
Determination of sulfur content
Voting begins on:
of automotive fuels — Ultraviolet
fluorescence method
Voting terminates on:
ICS: 75.160.20; 75.160.30
THIS DOCUMENT IS A DRAFT CIRCULATED
FOR COMMENTS AND APPROVAL. IT
IS THEREFORE SUBJECT TO CHANGE
AND MAY NOT BE REFERRED TO AS AN
INTERNATIONAL STANDARD UNTIL
PUBLISHED AS SUCH.
This document is circulated as received from the committee secretariat.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL,
© ISO 2025
TECHNOLOGICAL, COMMERCIAL AND
USER PURPOSES, DRAFT INTERNATIONAL
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
STANDARDS MAY ON OCCASION HAVE TO
ISO/CEN PARALLEL PROCESSING
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
BE CONSIDERED IN THE LIGHT OF THEIR
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
POTENTIAL TO BECOME STANDARDS TO
WHICH REFERENCE MAY BE MADE IN
or ISO’s member body in the country of the requester.
NATIONAL REGULATIONS.
ISO copyright office
RECIPIENTS OF THIS DRAFT ARE INVITED
CP 401 • Ch. de Blandonnet 8
TO SUBMIT, WITH THEIR COMMENTS,
CH-1214 Vernier, Geneva
NOTIFICATION OF ANY RELEVANT PATENT
Phone: [phone]
RIGHTS OF WHICH THEY ARE AWARE AND TO
PROVIDE SUPPORTING DOCUMENTATION.
Email: [e-mail]
Website: www.iso.org
Published in Switzerland Reference number
ISO/DIS 20846:2025(en)
ii
oSIST prEN ISO 20846:2025
ISO/DIS 20846:2025(en)
Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 2
4 Principle . 2
5 Reagents and materials . 2
6 Apparatus . 4
7 Sampling and sample handling . 5
8 Apparatus preparation . 5
9 Apparatus calibration and verification . 6
9.1 Multi-point calibration .6
9.2 One-point calibration .7
9.3 Verification . .8
10 Procedure . 8
11 Calculation . 9
11.1 Using multi-point calibration.9
11.2 Using one-point calibration .10
11.3 Calculation .10
12 Expression of results .10
13 Precision . 10
13.1 General .10
13.2 Repeatability,r .11
13.3 Reproducibility, R .11
14 Test report .11
Bibliography .13

iii
oSIST prEN ISO 20846:2025
ISO/DIS 20846:2025(en)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing Documents is normally carried out through ISO
technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental
and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the
International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types
of ISO documents should be noted. This document was drafted in accordance with the editorial rules of the
ISO/IEC Directives, Part 2 (see www.iso.org/directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of any patent
rights identified during the development of the document will be in the Introduction and/or on the ISO list of
patent declarations received (see www.iso.org/patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions
related to conformity assessment, as well as information about ISO's adherence to the World Trade
Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 28, Petroleum and related products, fuels and
lubricants from natural or synthetic sources.
This fourth edition cancels and replaces the third edition (ISO 20846:2019).
The main changes compared to the previous edition are:
— the extension of the application scope to include higher blends of biodiesel (FAME) from 50 % up to neat
FAME (B100),
— next, further instructions regarding the (validity of the) multi-point calibration have been implemented.

iv
oSIST prEN ISO 20846:2025
DRAFT International Standard ISO/DIS 20846:2025(en)
Petroleum and related products — Determination of sulfur
content of automotive fuels — Ultraviolet fluorescence method
WARNING — The use of this document can involve hazardous materials, operations and equipment.
This document does not purport to address all of the safety problems associated with its use. It is
the responsibility of users of this document to take appropriate measures to ensure the safety and
health of personnel prior to application of the document and fulfil other applicable requirements for
this purpose.
1 Scope
This document specifies an ultraviolet (UV) fluorescence test method for the determination of the sulfur
content of the following products:
— having sulfur contents in the range 3 mg/kg to 500 mg/kg,
— motor gasolines containing up to a mass fraction of 3,7 % (3,7 % (m/m) ) of oxygen [including those
blended with a volume fraction of ethanol up to about 10 % (10 % (V/V) )],
— diesel fuels, including those containing up to a volume fraction of about 50 % of fatty acid methyl
ester (FAME),
— having sulfur contents in the range of 3 mg/kg to 45 mg/kg,
— synthetic fuels, such as hydrotreated vegetable oil (HVO) and gas to liquid (GTL).
1)
— having sulfur contents in the range of 3 mg/kg to 30 mg/kg ,
— neat FAME (B100) and diesel fuels containing volume fraction of more than 50 % of FAME.
Other products (for example process feeds and effluents) can be analysed and other sulfur contents can be
determined according to this test method, however, no precision data for products other than automotive
fuels and for results outside the specified range have been established for this document. Halogens interfere
with this detection technique at concentrations above approximately 3 500 mg/kg.
NOTE 1 Some process catalysts used in petroleum and chemical refining can be poisoned when trace amounts of
sulfur-bearing materials are contained in the feedstocks.
NOTE 2 Nitrogen interference can occur, see 6.5 for further guidance.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes
requirements of this document. For dated references, only the edition cited applies. For undated references,
the latest edition of the referenced document (including any amendments) applies.
ISO 1042, Laboratory glassware — One-mark volumetric flasks
ISO 3170, Hydrocarbon Liquids — Manual sampling
ISO 3171, Petroleum liquids — Automatic pipeline sampling
ISO 3675, Crude petroleum and liquid petroleum products — Laboratory determination of density —
Hydrometer method
[6]
1) Based on ISO 4259-1 , the lowest acceptable single result that is deemed as a valid result is 1,4 mg/kg.

oSIST prEN ISO 20846:2025
ISO/DIS 20846:2025(en)
ISO 12185, Crude petroleum, petroleum products and related products — Determination of density —
Laboratory density meter with an oscillating U-tube sensor
3 Terms and definitions
No terms and definitions are listed in this document.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
4 Principle
A hydrocarbon sample is either directly injected or placed in a sample boat. Then, it enters a high temperature
combustion tube (1 000 °C to 1 100 °C), where the sulfur is oxidized to sulfur dioxide (SO ) in an oxygen-rich
atmosphere. Water produced during the sample combustion is removed and the sample combustion gases
are exposed to UV light. The SO absorbs the energy from the UV light and is converted to excited sulfur
dioxide (SO *). The fluorescence emitted from the excited SO * as it returns to a stable state SO is detected
2 2 2
by a photomultiplier tube and the resulting signal is a measure of the sulfur contained in the sample.
5 Reagents and materials
5.1 Inert gas, argon or helium, high purity grade with a minimum purity of 99,998 % by volume.
5.2 Oxygen, high purity grade with a minimum purity of 99,75 % by volume.
CAUTION — Oxygen vigorously accelerates combustion.
5.3 Solvent
5.3.1 General
Use either that specified in 5.3.2 or 5.3.3, or a solvent similar to that occurring in the sample under analysis.
Correction for sulfur contribution from solvents used in standard preparation and sample dilution is
required. Alternatively, use of a solvent with non-detectable sulfur contamination relative to the unknown
sample makes the blank correction unnecessary.
NOTE Non-detectable is in general considered to be below 0,5 mg/kg for regular samples, though solvents with <
0,05 mg/kg of sulfur are readily available.
5.3.2 Toluene, reagent grade.
5.3.3 Isooctane, reagent grade.
CAUTION — Flammable solvents.
5.4 Sulfur compounds
5.4.1 General
Compounds with a minimum purity of 99 % by mass. Examples are given in 5.4.2 to 5.4.5. Where the purity
of these compounds is less than 99 % by mass, the concentrations and nature of all impurities shall be
established.
NOTE 1 A correction for chemical impurity can be applied when the sulfur content is known with accuracy.

oSIST prEN ISO 20846:2025
ISO/DIS 20846:2025(en)
[3]
NOTE 2 Certified reference materials (CRM) produced in accordance with ISO 17034 are suitable alternatives to
the compounds listed in 5.4.2 to 5.4.5.
5.4.2 Dibenzothiophene (DBT), of molar mass 184,26 g/mol, with a nominal sulfur content of 17,399 %
mass fraction.
5.4.3 Dibutyl sulfide (DBS), of molar mass 146,29 g/mol, with a nominal sulfur content of 21,915 % mass
fraction.
5.4.4 Dibutyl disulfide (DBDS), of molar mass 178,36 g/mol, with a nominal sulfur content of 35,950 %
mass fraction.
5.4.5 Thionaphthene (benzothiophene) (TNA), of molar mass 134,20 g/mol, with a nominal sulfur
content of 23,890 % mass fraction.
5.5 Sulfur stock solution
Prepare a stock solution of approximately 1 000 mg/l sulfur content by accurately weighing the appropriate
quantity of sulfur compound (5.4) in a volumetric flask (6.9). Ensure complete dissolution with solvent (5.3).
Calculate the exact sulfur concentration of the stock solution to the nearest 1 mg/l. This stock solution is
used for the preparation of calibration standards. As an alternative procedure, a sulfur stock solution of
approximately 1 000 mg/kg can be prepared by accurately weighing the appropriate quantity of sulfur
compound (5.4) in a volumetric flask (6.9) and reweighing the volumetric flask once it has been filled to
the mark with the solvent (5.3). Take precautions to ensure that evaporation of the solvent and/or sulfur
compounds is not causing weighing errors.
The appropriate mass of sulfur compound described in 5.4.2 to 5.4.5 to add to the 100 ml flask is 0,574 8 g
(DBT), 0,456 3 g (DBS), 0,2781 g (DBDS) and 0,418 6 g (TNA).
NOTE The shelf life of the stock solution is approximately three months when stored at low temperature, typically
in a refrigerator.
5.6 Calibration standards
Prepare the calibration standards by dilution of the stock solution (5.5) with the selected solvent (5.3).
Calculate the exact sulfur content of each calibration standard.
Calibration standards with a known sulfur concentration, in milligrams per litre, (or content, in milligrams
per kilogram) can be obtained with a volume/volume dilution (or mass/mass dilution, respectively) of the
stock solution at 1 000 mg/l (or 1 000 mg/kg respectively). Other practices are possible, but those mentioned
above avoid any density correction.
New calibration standards should be prepared on a regular basis, depending upon the frequency of use and
age. When stored at low temperature, typically in a refrigerator, the calibration standards with a sulfur
content above 30 mg/kg (or mg/l) have a shelf life of at least one month. Below this sulfur content (30 mg/
kg), the shelf life should be reduced.
5.7 Quality control samples
Quality control samples are stable samples representative of the materials being analysed, which have a
sulfur content that is known by this test method over a substantial period of time. Alternatively, there are
standard materials with a certified value commercially available. Prior to use, ensure that the material is
within its shelf life.
5.8 Quartz wool
Follow the manufacturer's recommendations.

oSIST prEN ISO 20846:2025
ISO/DIS 20846:2025(en)
6 Apparatus
Figure 1 illustrates the basic pieces of the ultraviolet fluorescence equipment.
Key
1 UV source
2 photomultiplier
3 output signal
4 furnace (6.1)
5 oxygen input
6 inert gas input
7 gases output
8 vapour drier (6.4)
9 quartz tube
10 microlitre syringe
Figure 1 — Synopsis of the apparatus
6.1 Furnace, comprising a device capable of maintaining a temperature sufficient to pyrolyze all of the
sample and oxidize all sulfur to sulfur dioxide (SO ).
It can be set either in a horizontal or vertical position.
6.2 Combustion tube, of quartz, constructed to allow the direct injection of the sample into the heated
oxidation zone of the furnace (6.1).
The combustion tube shall have side arms for the introduction of oxygen and carrier gas. The oxidation
section
...